<!DOCTYPE html>
<html lang="en-US">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width">
    <title>Box model</title>
    <link rel="stylesheet" href="style.css">
  </head>
  <body>
    <header>Header</header>
    <main>Main content</main>
    <footer>Footer</footer>
  </body>
</html>
